In order to enhance the whiteness of a white background after processing, application of a fluorescent whitening agent is a well-known technique. Acceptable visual whiteness varies depending on personal preference. However, generally, it is known that white tinted with blue looks more white than achromatic white. In order to prepare such white, the application of the fluorescent whitening agent is an important technique.
In recent years, a silver halide light-sensitive photographic material has been required which can be applied to simple and quick processing. Particularly, in a silver halide light-sensitive color photographic material, color photographic processing has been increasingly simpler and quicker, and quick processability and stability in processing have also been required. Particularly, in color photographic paper which is highly required to achieve quick development, as an applied silver halide emulsion, an application technique of a silver halide emulsion having a high content ratio of silver chloride, which exhibits improved developability, has been developed to markedly shorten processing time.
Furthermore, in view of environmental protection, the decrease in processing solution wastes is strongly required for processing of sliver halide light-sensitive materials. Due to this, a continual decrease in the replenishment rate of processing solutions has been progressed.
However, in such quick processing carried out in a short period of time and at a low replenishment rate, residual staining due to sensitizing dyes and other dyes, is likely to occur. Under such conditions, improvement in whiteness employing a fluorescent whitening effect becomes increasingly important in order to provide photographic paper which produces a pleasing appearance of prints.
Needless to say, of course, irrespective of the presence of residual staining, the florescent whitening method is generally employed to improve visual perceived whiteness.
Such fluorescent whitening methods known in the art include, for example, methods in which a fluorescent whitening agent is incorporated into the paper support or a polyethylene laminated layer thereof, as disclosed in Japanese Patent Publication Open to Public Inspection No. 53-117, U.S. Pat. Nos. 3,449,257, 3,501,298, and 3,558,316,; furthermore, methods in which a water-soluble fluorescent whitening agent is directly added to a silver halide emulsion layer or another photographic coating constituting layer, as described in Japanese Patent Publication No. 48-30495, etc.; or methods in which an oil-soluble fluorescent whitening agent is dissolved in a high boiling point organic solvent, is emulsify-dispersed, and the resulting dispersion is added, as described in U.K. Patent No. 1,072,915, U.S. Pat. No. 2,322,027, Japanese Patent Publication No. 4-81783, etc.; and methods in which a polymer in which a fluorescent whitening agent is mixed is added, or a fluorescent whitening agent is dissolved and dispersed at the same time when a photographic dispersing agent such as a coupler, etc. is dispersed and added; or for example, a fluorescent whitening agent such as a water-soluble diaminostilbene series derivative is previously added to the developing solution and the fluorescent whitening agent penetrates into the light-sensitive material, as disclosed in Japanese Patent Publication Nos. 45-37376, 45-11111, and 51-47043, and U.S. Pat. Nos. 3,416,923 and 3,418,127.
However, in the case of polyethylene-laminated paper suitable for quick processing, when a fluorescent whitening agent intends to be contained in the laminated layer, defects result such that during the thermal extrusion process at the formation of the lamination layer, the fluorescent whitening agent is easily decomposed, or due to insufficient heat resistant sublimating properties of a fluorescent whitening agent, the adhesion to equipment causes production problems. In addition, in this method, in order to prepare many types of light-sensitive materials to meet application requirements, the amount of the fluorescent whitening agent to be added requires adjustment over a long time, increases labor and cost, and due to the limitation for the application, only a few are employed for production.
In the method in which a water-soluble fluorescent whitening agent is added to a silver halide emulsion layer or other photographic coating constituting layers, defects are caused such that the age n t is dissolved out to a developing solution and whiteness is not improved as expected, and whiteness varies in accordance with processing conditions.
In order to minimize the outflow to a developing solution, a method was considered in which, after an oil-soluble fluorescent whitening agent was dissolved in a high boiling point organic solvent, the addition was carried our upon emulsifying and dispersing the resulting. However, defects were caused such that sufficient whiteness was not obtained due to an insufficient whitening effect, or during production or storage, whiteness was degraded due to the deposition or decomposition, and in addition, staining resulted occasionally.
Furthermore, the method, in which a fluorescent whitening agent was previously added to the developing solution, caused problems such that when the amount necessary for obtaining a sufficient fluorescent whitening effect was added, the fluorescent whitening agent deposited during the elapse of time and the deposited agent adhered to a light-sensitive material to degrade the quality.
As mentioned above, at present, techniques for improvement in whiteness employing a fluorescent whitening agent result in no sufficient effect to the silver halide light-sensitive photographic material.
Hence, investigation has been carried out and it has been found that the above-mentioned defects are improved by incorporating a fluorescent whitening agent as fine solid particles into a silver halide light-sensitive emulsion layer or a non-sensitive hydrophilic colloidal layer.
Furthermore, along with the proliferation of light-sensitive color photographic materials, requirements for quality images has been increasingly demanded in addition to the above-mentioned improvement in whiteness. In such situations, regarding the light-sensitive material for photographic color prints, investigations on color reproduction, tone reproduction, improvement in sharpness, improvement in uneven density, etc. have been conducted more widely than before.
As factors affecting sharpness, irradiation and halation have been generally known. The former is generated by the fact that incident light is scattered by silver halide grains or coupler droplets dispersed into a gelatin layer, and the degree thereof depends mainly on the amount of gelatin, the amount of silver halide, the amount of oil droplets, and furthermore, the latter depends on the amount of reflection light from a support, the reflectance and refractive index of the support.
Antiirradiation has been carried out for improvement in dyes. Techniques to improve these are described, for example, in Japanese Patent Publication Open to Public Inspection Nos. 50-145125, 52-20830, 50-111641, 61-148448, 61-151650, 62-275562, 62-283336, etc.
Regarding the minimization of halation, a method is known in which an antihalation layer is provided. Techniques for this improvement are described, for example, in Japanese Patent Publication Open to Public Inspection Nos. 55-33172, 59-193447, 62-33448, etc.
Based on these techniques, sharpness is improved. However, sensitivity is markedly decreased. It has been difficult to improve the sharpness, while maintaining sensitivity high enough for practical use.
Furthermore, it is known that sharpness is improved by incorporating black colloidal silver into a layer lower than the dye forming layer. However, when a large amount of colloidal silver is employed to markedly improve sharpness, the white background is deteriorated due to insufficient silver removal. It has been difficult to employ this technique to improve the sharpness.
As for the sharpness, deterioration is remarkable at longer wave length, especially infrared area. So, it is difficult to improve sharpness of a silver halide light sensitive material having infrared sensitivity, which has become popular.
Accordingly, an investigation has been conducted and it is found that by incorporating fine solid particles of a fluorescent whitening agent into a nonlight-sensitive hydrophilic colloidal layer provided in a specified position, excellent sharpness is obtained and the whiteness and lightness of a background are improved.